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I've got a gut-related condition and saw this claim on the BBC

[The stomach's] complex work is under the control of what's sometimes called "the little brain", a network of neurons that line your stomach and your gut. Surprisingly, there are over 100 million of these cells in your gut, as many as there are in the head of a cat.

The little brain does not do a lot of complex thinking but it does get on with the essential daily grind involved in digesting food - lots of mixing, contracting and absorbing, to help break down our food and begin extracting the nutrients and vitamins we need.

It seems profoundly unlikely to me that the human digestive system requires as many neurons as an entire small animal. Are there really so many neurons in the human gut?

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    en.wikipedia.org/wiki/Enteric_nervous_system could be an answer or a second reference for the question, as it mentions the false cat brain equivalence. If you really want to make sure there are as many neurons in your belly as in a cats head, just eat a cat.
    – daniel
    Sep 1, 2017 at 7:03
  • @daniel: If you think it is false, please provide an answer with a reference supporting that view.
    – Oddthinking ♦
    Sep 1, 2017 at 7:06
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    @Oddthinking I am not a neurosurgeon but I think the false equivalence (bad comparison? not the argument type) is because they are different types of neurons, not the ones we associate with 'I think therefore I am" but the ones that are analogous to strain gauges or communication cables.
    – daniel
    Sep 1, 2017 at 7:35
  • With other words, implicit claim again. It might be true or not, but it doesn't mean your guts are as "intelligent" as a cat. Answering the number of neurons doesn't cover the implicit claim.
    – DevSolar
    Sep 1, 2017 at 9:56
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    "That's where the truth lies, right down here in the gut. Do you know you have more nerve endings in your gut than you have in your head? You can look it up. Now, I know some of you are going to say, "I did look it up, and that's not true." That's 'cause you looked it up in a book. Next time, look it up in your gut. I did. My gut tells me that's how our nervous system works." - Steven Colbert
    – corsiKa
    Sep 1, 2017 at 19:06

1 Answer 1

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From the claim:

Surprisingly, there are over 100 million of these cells in your gut

New Scientist states "estimated 500 million neurons".

From the claim:

...as many as there are in the head of a cat.

"Evolution of the brain and intelligence" by Gerhard Roth and Ursula Dicke in "Trends in Cognitive Sciences Vol.9 No.5 May 2005" lists the number of cortical neurons in a cat as 300 million (table 1, page 251).

For ballpark figures like this, I usually settle for "same order of magnitude", and would state the claim is probably true.

Note this doesn't make any claims about the relative intelligence of the human gut vs. a cat.

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    Shoutout to @daniel, the above sources are only one or two clicks away from his WP link on the question subject.
    – DevSolar
    Sep 1, 2017 at 10:48
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    What fraction of brain neurons are cortical neurons? If it is 1/3, then cats have roughly 1000 million total neurons, and your answer is valid. If it is a much smaller fraction, like 5%, then cats have 6000 million neurons; an order of magnitude more than the 500 million in the gut.
    – BobTheAverage
    Sep 1, 2017 at 15:43
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    Plus cats have a lot of neurons dedicated to "being a bastard."
    – PoloHoleSet
    Sep 1, 2017 at 15:59
  • @BobTheAverage: "Cortical" means "of the (cerebral) cortex" (which is responsible for the higher cognitive functions), i.e. what is commonly referred to as "the brain" a.k.a. "in the head" as per the question. Yes, there's also the cerebellum and the brain stem.
    – DevSolar
    Sep 1, 2017 at 16:16
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    So how many neurons are there in a ca'ts stomach? (Disregarding any belonging to recently consumed mice or small birds, of course.)
    – jamesqf
    Sep 1, 2017 at 19:33

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